Navigational guidance devices are an integral part of smart munitions, which can be implemented as rockets, missiles, and bombs. Until recently, these guidance devices have had insufficient techniques to test their survivability and functionality in a laboratory setting. For example, high speed centrifuges (at tens of thousands of G's) allow for testing of low frequency quasi-static loads applied to guidance devices during the initial phase of gun or rocket launch. In addition, solenoid actuated mechanical impact shock and pyroshock have been used to simulate the dynamics of fin deployment. Vibration and low G centrifuge have also been used to test maneuvering of the projectile during its mission.
Nevertheless, there are few good options for testing the high amplitude, high frequency dynamic shock environment that is caused by hot propellant gases expanding as the projectile leaves the gun barrel or muzzle. One laboratory method intended to replicate the muzzle exit shock is a pyrotechnic shock, but this method has several shortcomings. This method requires expendable explosive materials, and can also be destructive to test holding fixtures. In addition, this method requires a long lead time for setup (e.g., months), has poor repeatability, has difficulty in tuning the shock profile, and results in high measurement errors.
Another laboratory method uses pneumatics to produce the shock. A unit under test is exposed to the shock as a deceleration upon impact of the unit and a honeycomb or other deformable structure downstream. Often times in pneumatic shock applications, a section of a barrel is required to be under vacuum in order for the unit under test to reach a high enough velocity. This requires a disposable membrane to be punctured as a pressure barrier during the test. That particular pneumatic method is undesirable because it requires to dispose and replace test equipment parts.
Another muzzle exit testing option is to use the U.S. Army's soft catch howitzer gun (SCat gun) at the Picatinny Arsenal or similar test facilities. This option, however, is an overtest due to soft catch mechanisms, has a high cost, does not include a unit under test power on sequence, does not have a quick turn around on data collection (weeks), allows only for a small sample size, and does not only test the muzzle exit portion of the mission timeline.
Further methods of muzzle exit testing include field testing, such as proving ground testing or flight testing. These methods, however, have high risk, high cost, limited repeatability, and high visibility due to testing at the customer level. In addition, field testing requires a unit under test to be mounted within an expendable projectile, burns propellant to accelerate, may require an expendable method of stopping the projectile, or may not return a functional or structurally intact unit under test, for further testing and observation, due to impact damage. In addition, waiting to test shock robustness until a flight test can cost over one million dollars for the test, plus heightened visibility, and if a failure occurs, a costly amount of product redevelopment is required.